How to improve my marks

Hey everyone. I need some advice on how I could possibly go about prepping for exams in order to improve my marks.

So a little bit of background: I've applied twice now to several medical schools in my country (South Africa), and failed to get in on both occasions. This year would be my third attempt at applying for medicine.

On both occasions, I prepared on my own for exams, gathered resources on my own, basically did everything by myself without a tutor/teacher. And although I've managed to get decent marks, they aren't nearly competitive enough for what med school.

At the moment I am also working, and although my hours are flexible, most of my free time is at night, after work (unless I have a day or two off). I'm contemplating getting the help of a tutor for two of my subjects (Maths and Physics), but am unsure if this would really make a difference in my performance since my exams are 3 months away.

As I am also studying on my own again, I am also weary of not performing well again. Is there anyone that might have a similar situation/have gone through a similar situation, or otherwise, is there any suggestions as to how I can dramatically improve on my results?